The invention pertains to a carburetor for an internal combustion engine, particularly a two-cycle engine which is provided with a suitable rotary throttle valve and used as the driving power source for chain saws and trimmers.
It is known to use, for internal combustion engines, a carburetor with a cylindrical rotary throttle valve. By rotation of the rotary throttle valve, it is possible to change the effective diameter of the air passage serving as the venturi bore which opens in the direction of the diameter of the throttle valve, and which cooperates with the air passage that is provided in the carburetor body in which the throttle valve is located. In rotating the throttle valve, the quantity of the fuel from the fuel nozzle entering the venturi bore can be controlled. This rotating operation of the throttle valve of the carburetor provides excellent engine response in normal operation of the internal combustion engine.
However, when the throttle valve is in an idling position, the intake air flow speed through the venturi bore diminishes, and thus reduces the fuel atomization. When an engine is idling at a certain position of the carburetor, it is difficult to provide a proper fuel supply to the internal combustion engine through the nozzle. This causes a quantity of liquid fuel to collect in the venturi bore. With the exception of the idling function, the carburetor, regardless of its position, can control an internal combustion engine very effectively and with good response. But as pointed out, the operating efficiency at idling in certain positions is not ideal. In particular, when said carburetor position is in an upside down position, liquid fuel may collect in the venturi bore and then on occasion be quickly sucked into the internal combustion engine which may cause the engine to stop.
Because of this problem, the existing carburetor with the rotary throttle valve cannot be utilized with an internal combustion engine of a chain saw or trimmer which is expected to maintain good performance at any and all positions of the carburetor. Therefore, its application area has been limited.
The objective in this invention is to eliminate this defect of the rotary throttle valve carburetor and to offer a new rotary throttle system carburetor which can properly control an internal combustion engine in any position through the stages of full throttle or idling.
The invention relates to a cylindrical throttle in general and the venturi bore opens in the direction of the diameter of the cylinder. The outside of the throttle valve, where said venturi bore of the rotary throttle valve opens, is provided with porous material.
The distinctive feature of the invention is that while idling at certain positions, when fuel tends to collect in the venturi bore, the porous material will absorb liquid fuel and prevent fuel collection in the venturi bore.
The novelty of the invention can be further made clear by the following explanation and in the drawings which illustrate various embodiments.